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.\" Copyright (c) 2016 Alexander Motin <mav@FreeBSD.org>
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.Dd September 2, 2017
.Dt IF_NTB 4
.Os
.Sh NAME
.Nm if_ntb
.Nd Virtual Ethernet interface for Non-Transparent Bridges
.Sh SYNOPSIS
To compile this driver into your kernel,
place the following lines in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "device ntb"
.Cd "device ntb_transport"
.Cd "device if_ntb"
.Ed
.Pp
Or, to load the driver as a module at boot, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
if_ntb_load="YES"
.Ed
.Pp
The following tunables are settable from the
.Xr loader 8 :
.Bl -ohang
.It Va hw.if_ntb.num_queues
Limits maximal number of queues per interface.
Default is unlimited.
.El
.Sh DESCRIPTION
The
.Nm
driver attaches on top of the
.Xr ntb_transport 4
driver to utilize one or more of its packet queues to create virtual
Ethernet network interface between the systems.
Typical MTU for the interface is about 64KB to reduce overhead.
Default MAC address for the interface is randomly generated.
.Pp
The
.Nm
driver does not implement any real hardware offload, but since PCIe link is
protected by CRC32, in some situations it may be possible to save some CPU
cycles by enabling fake checksum offload on both link sides via setting
.Cm rxcsum
and
.Cm txcsum
interface options.
.Sh SEE ALSO
.Xr ntb_transport 4
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was developed by Intel and originally written by
.An Carl Delsey Aq Mt carl@FreeBSD.org .
Later improvements were done by
.An Conrad E. Meyer Aq Mt cem@FreeBSD.org
and
.An Alexander Motin Aq Mt mav@FreeBSD.org .
.Sh BUGS
Linux supports only one queue per interface, so manual configuration
may be required for compatibility.
